Logical unit configuration for HDS Lightning

Logical unit (LU) configuration for HDS Lightning supports both RAID 1 and RAID 5 arrays.

The HDS Lightning system can have up to 8192 LUs defined; however, only 256 LUs can be mapped to a single port. Report LUNs is supported by LUN 0, so the Storwize® V3500 system can detect all LUNs.

In the event that a LUN 0 is not configured, the HDS Lightning system presents a pseudo-LUN at LUN 0. The inquiry data for this pseudo-LUN slightly differs from the inquiry data of normal LUNs. The difference allows the Storwize V3500 system to recognize the pseudo-LUN and exclude it from I/O. The pseudo LUN can accept the report LUNs command.

The HDS Lightning system supports both open-mode attachment and IBM zSeries attachment. The emulation mode is set when the LU is defined. All LUNs that are presented to the Storwize V3500 system must use open emulation. All LUNs with open emulation use a standard 512 byte block size.

The HDS Lightning system can only have certain sized LUs that are defined. These LUs can be expanded by merging 2 - 36 of these LUs using the Logical Unit Size Expansion (LUSE) feature. They can also be made into several smaller virtual LUNs by using the Virtual LVI/LUN feature.

Special LUs

When an LU is mapped to a host, you have the option to make it a command LUN. Command LUNs support in-band configuration commands, but not I/O. Therefore, you cannot map command LUNs to the Storwize V3500 system.